[QE] - Investigation of JenkinsPipelineUnit framework.

Currently, we are facing problem with many pipelines/jobs which has different paths of using methods, envs, etc. Moreover, with each refactor even small ones arise problems with wrong configuration, a bad set of environment variables and so on. This should be somehow tested on unit-level. This verification eliminates copy-paste or previously mentioned errors. One of the solutions is to use JenkinsPipelineUnit which can mock pipelines, sh commands and much more...

Some useful links:

• https://github.com/jenkinsci/JenkinsPipelineUnit
• https://gitter.im/JenkinsPipelineUnit/Lobby?at=5f3d10bb33878e7e602c1131